(57) A microwave balun using TEM wave guides, consists of two second-order reactance sections
of electrical lengths equal to about a quarter of the wavelength of a radiofrequency
signal comprising an unbalanced input-port and a balanced output-port. Each section
(I, II) comprises two strips of microstrip-like wave guides, placed in such a way
above the ground plane being the bottom metallization (0) of the lower layered substrate
(3) that one of the guides (1, 2) is on the top side of the lower substrate, and the
other guide (1', 2') placed thereabove is separated therefrom by the material volume
of the upper layered substrate (4) and is on the top side of the upper substrate.
The pair of guides, any one from each section, being the pair of input guides (1,
2) is connected with each other by two ends (12, 21), while one of the two remaining
ends (11) thereof is connected to the input-port (10), and the other one (22) is terminated
for a radio-frequency signal by a reflecting element. The second pair of the remaining
wave guides (1', 2') being the pair of output guides, forms with two ends (12', 21'
) thereof, one from each section, a pair of output-port terminals. Each of the remaining
ends (22', 11') of the pair of output guides is terminated for a radio-frequency signal
by a reflecting element, whereby phases of the said reflecting elements are dependent
on the configuration choice of the input and the output-ports and the phase choice
of the reflecting element terminating the end of input guides, the opposite one to
the input. The cross-section dimensions and material constants of materials used have
the values dependent on the required broadband properties according to the set of
transmission-reflection parameters of the balun and the required input and output
impedance. The balun design according to the invention is designed for utilization
within the frequency range of 1-18 GHz.
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